CN1188309C - Vehicle air braking systems - Google Patents

Abstract

An electronic control system for the compressor of a vehicle air braking system, the control system having one or more inputs indicative of a vehicle operating state, and an output for determining whether a compressor is on-load or off-load, the system further including target means to calculate in real time a target pressure for a reservoir downstream of said compressor, said output being responsive to said target means. The target pressure may be varied in real time to suit vehicle running conditions and permits a small but significant reduction in vehicle fuel consumption by driving the compressor when the vehicle is likely to be coasting or slowing down.

Description

vehicle air brake

technical field

The present invention relates to a vehicle pneumatic braking device, and more particularly to the electronic control of the air compressor used in the system.

Background technique

A typical air brake unit includes: a compressor, a compressed air reservoir, a driver operated by a command valve, and a number of air actuators for vehicle braking. The system typically includes a dryer for the compressor output gas, and controls to unload the compressor when the pressure in the air receiver reaches a maximum and the valve is commanded to close. The compressor is usually idling by unloading the compressor by temporarily opening the outlet to atmosphere. On the other hand, the compressor may also include a clutch connected to its drive source (usually the engine of the vehicle).

Compressors absorb a considerable amount of energy, so it is best to minimize their operating hours while ensuring that there is enough compressed air to meet demand. Usually this is achieved in part by minimizing the "dead" volume on the high pressure side of the command valve.

The compressor control system exists because the control of the compressor is responsive to one or more sensed vehicle operating conditions. These control systems operate between preset upper and lower brake system air pressures.

The required control system can better determine the operating time of the compressor based on the predicted demand and the real-time operating status of the vehicle.

Contents of the invention

According to a first aspect, the present invention provides an electronic control system for a compressor of a vehicle air brake system having one or more input signals indicative of vehicle operating conditions and an output signal determining whether the compressor is loaded or unloaded , the system further includes a rated device for calculating the rated pressure of the air storage tank downstream of the compressor in real time, and the output signal will be responded by the rated device.

An advantage of the present invention is that the rated pressure can be changed in real time to suit the operating conditions of the vehicle. For example, the rated pressure may be higher in closed throttle mode than in open throttle mode. The rated pressure may be directly dependent on the predicted demand of the vehicle's braking system, or may directly relate to related factors such as the temperature of the gas delivered from the compressor.

The input signal to the control system can consist of one or more of the following variables: engine speed, vehicle speed, vehicle throttle opening, air pressure in the brake system air reservoir, gas temperature at the output of the air compressor, relative The dryness of the dryer desiccant downstream of the compressor, the dryness of the gas downstream of the air dryer, etc.

In a preferred embodiment, the control system includes: a first input signal representing vehicle engine speed, a second input signal representing vehicle speed, a third input signal representing vehicle throttle opening, and a compressor A fourth input signal for the air pressure at the lower end of the air reservoir, the rated pressure in closed throttle mode is higher than the rated pressure in open throttle mode.

In this specification, the term "throttle" is used in reference to a vehicle's accelerator control pedal or other device for controlling fueling of a vehicle.

The system requires a higher rated pressure in closed throttle mode when the vehicle is likely to coast or slow down. In this case, the driver typically releases the accelerator pedal to close the throttle, and the vehicle's momentum drives the engine and compressor. The energy to drive the compressor is "free" in this mode, at least in the sense that no fuel is burned. Additionally, compressor loading decelerates the vehicle further, but this result is only useful if accompanied by off-throttle mode or followed by braking. To take full advantage of the rated pressure in the gas reservoir in closed throttle mode, it can be adjusted up to a higher than normal level, which reduces compressor operating time during open throttle mode.

The invention only needs a slight adjustment to the existing electronic control system, so that the fuel consumption of the vehicle can be slightly but significantly reduced.

In a preferred embodiment, the higher rated pressure is 8-10% higher than the normal rated pressure. The system can also include a third higher pressure rating to meet the high pressure needs of associated gas systems such as air suspension.

A particular advantage of the invention is that there is a higher nominal pressure in braking (throttle valve closed) mode, and that there is also a final purge of common gas dryers in the air reservoir at the last braking before the engine is switched off additional air volume. This is very useful as it keeps the air brakes clean and dry at the end of the working day. Also, the vehicle air intake system was clean and dry at the start of the second working day.

It is preferable to provide separate control systems for the compressor and the purge valve. This ensures that the air supply line connected to the compressor and purge valve/reservoir is not depleted each time the purge valve is activated. Obviously, if the air line is depleted (which it has been so far) then the compressor will need to work longer when loaded.

Conversely, the normal rated pressure can also be reduced. For example, if the compressed air at the output of the compressor is hot due to ambient conditions such as heat combined with high demand for gas (and thus high compressor operating hours), it may come close to damaging the desiccant in common gas dryers. temperature. In this case, it may be necessary to reduce the normal rated pressure, thereby reducing the operating time of the compressor, and allowing the temperature of the compressor to drop.

The control system preferably also includes an overload device to ensure that a lower rated pressure is not applied under conditions requiring the maximum amount of gas, such as during hard braking.

According to a second aspect, the present invention provides a control system for a compressor of a vehicle's air brake system, the compressor being unloaded at a predetermined rated pressure, the control system having an input signal indicative of the throttle position of the vehicle and capable of The adaptation increases the rated pressure in real time at zero throttle opening.

According to a third aspect, the present invention provides a control system for a compressor of a vehicle air brake system, the control system having a first input signal indicative of vehicle engine speed, a second input signal indicative of vehicle speed, a second input signal indicative of vehicle knot A third input signal of valve opening, a fourth input signal representing the air pressure at the lower end of the air storage tank of the compressor, and an output signal for determining whether the compressor is loaded or unloaded, and the system further includes a real-time calculation of the rated pressure of the air storage tank device, the rated pressure is higher in closed throttle mode than in open throttle mode.

According to a fourth aspect, the present invention provides a method for controlling a compressor of a vehicle air pressure brake system, the method comprising the following steps:

providing a compressor control system having one or more inputs indicative of vehicle operating conditions,

An output signal is provided from the control system to enable the compressor to be loaded or unloaded depending on the vehicle operating state,

Rating means are provided for calculating the rated pressure at the lower end of the compressor air receiver, wherein the output signal of the control system is responsive to the rating means.

In a preferred embodiment, said input includes a first input signal representing vehicle engine speed, a second input signal representing vehicle speed, a third input signal representing vehicle throttle opening, and a A fourth input signal representing air pressure within the air reservoir.

Description of drawings

From the following description of a preferred embodiment in conjunction with the accompanying drawings, the features of other aspects of the present invention will emerge,

Figure 1 is a graph showing typical compressor pressure ratings in relation to vehicle operating modes.

In the figures, the X-axis represents vehicle operating modes, while the Y-axis represents pressure. A narrow solid band indicates the rated pressure. As shown in the figure, the solid line indicates that the compressor is idling, the dotted line indicates purification, and the dashed line indicates that the compressor is pumping air.

Detailed ways

In a typical air brake unit, compressor output air is directed through a check valve and air dryer to an air reservoir. The dry air in the air reservoir is periodically directed back into the air dryer (usually including a bed of drying material) to remove most of the moisture from it. The purge process can be controlled by a timer and takes place after the compressor has been loaded for a predetermined time. Since the system's demand for gas quantity exceeds the demand for quality, the purification process is usually not performed during the vehicle braking mode; and the braking process is usually very short.

Referring to the accompanying drawings, the vehicle is first shown at a standstill; the engine is not operating. The remaining system pressure is low and the compressor is idling (actually stopped). Nominal pressures are plotted, but their values are not critical.

Then, the engine is started and is idling. The nominal pressure is immediately at a normal level; in this example it is just above 9×10 ⁵ Pa (9 bar). As shown in the figure, the compressor works in two stages, with a timed cleaning process inserted in between; the pumping stage of the compressor can be more or less according to demand. Other control systems ensure that the vehicle is not driven until it reaches a safe operating pressure.

After reaching the target position, the compressor is unloaded; system pressure may or may not drop, depending on system gas usage or leakage, such as air suspension or front window wiper operation.

The pressure target usually has a hysteresis to avoid continuous switching of the compressor between loading and unloading, and this is represented by the width of the rated pressure band.

During drive mode, the compressor is loaded as needed and can also perform a purge process if necessary. The pressure value may fluctuate slightly between idle mode and drive mode for the purge process.

Then, in overload mode, the indicated nominal pressure increases to approximately 10 ⁴ Pa (10 bar). Adjust to a higher rated pressure according to system requirements, and can be greater or less than 10 ⁴ Pa (10 bar). In this mode, no fuel is used to drive the compressor. As before, a pumping and purge process occurs. The same happens in brake mode, except that purge is canceled.

In the next idle mode, the pressure target drops to normal again. The compressor does not begin loading again until the air receiver pressure has dropped to the bottom of the normal band. A purge cycle after braking is shown in this phase, which is a normal process initiated by the control system to compensate for the lack of purge during braking.

The lower pressure target also occurs during another cycle of drive mode.

An ECAS procedure is then shown. This process occurs when an associated gas system such as a vehicle's air suspension requires a pressure higher than normal operating levels. The compressor will try to hit the new target, but, as shown, the consumption of gas is fairly close to the supply, so there is only a slight pressure increase when the ECAS event terminates.

Another idle mode is then shown and begins with a purge cycle due to reduced purge during an ECAS event.

Eventually, the vehicle and engine stopped working. The nominal pressure is reduced to an insignificant minimum value selected by the control software. High residual pressure allows for a final shutdown purge, leaving a clean dry inactive system. It is beneficial for the residual pressure to remain in the system as it avoids the inhalation of unclean and dry gas.

This specification describes some typical driving processes and is not intended to be exhaustive. An important feature is the higher pressure target during closed throttle mode.

Claims (13)

1. A control system for a compressor of a vehicle air brake system, the control system has one or more input signals representing the operating state of the vehicle, and an output signal for determining whether the compressor is loaded or unloaded, the system is further including rating means for calculating a rated pressure downstream of said compressor air receiver, said output signal being responsive to the rated pressure of the rated means such that when the air receiver pressure reaches the rated pressure, the compressor is unloaded and when the rated pressure Above the air reservoir pressure, the compressor loads. 2. The control system of claim 1 wherein one of the input signals to the control system is vehicle throttle position. 3. The control system of claim 2 wherein the rated pressure in closed throttle mode is higher than the rated pressure in open throttle mode. 4. The control system of claim 3, wherein said higher rated pressure is 8-10% higher than the normal rated pressure. 5. The control system of claim 4, further comprising a third higher rated pressure. 6. The control system of claim 1 wherein one control system input signal is the temperature at the output of the compressor. 7. The control system according to claim 6, wherein the rated pressure decreases as the temperature at the output end of the compressor increases. 8. The control system according to claim 1, wherein the compressor can be unloaded at a predetermined rated pressure, and the input signal to the control system includes an input signal representing the throttle position of the vehicle, which can be set at zero knots. Increase the rated pressure at the valve opening. 9. The control system according to claim 1, wherein the input signals of the control system include a first input signal representing vehicle engine speed, a second input signal representing vehicle speed, a vehicle throttle A third input signal for opening, and a fourth input signal indicative of air pressure at the lower end of the compressor air reservoir, wherein the rated pressure in closed throttle mode is higher than the rated pressure in open throttle mode. 10. A control system as claimed in claim 9, characterized in that said higher rated pressure is 8-10% higher than the normal rated pressure. 11. A control system as claimed in claim 10 further comprising a third higher rated pressure. 12. A control system as claimed in any preceding claim which provides separate control of the compressor and purge valve. 13. A method for controlling a compressor of a vehicle air pressure brake system, the method comprising the following steps: providing a compressor control system with one or more input signals indicative of the operating state of the vehicle, Make the rated device calculate the rated pressure at the lower end of the air storage tank of the compressor in real time; The control system provides an output signal to load or unload the compressor according to the operating state of the vehicle, wherein the output signal of the control system responds to the rated pressure of the rated device, so that when the pressure of the air storage tank reaches the rated When the rated pressure is higher than the air receiver pressure, the compressor is loaded.